Prostate cancer is the most common cancer among European and American men. Treatment of prostate cancer commonly involves surgical therapy including radical prostatectomy. However, despite the increasing use of nerve-sparing techniques, such as robot-assisted surgery, urinary incontinence and erectile dysfunction remain major adverse consequences of radical prostatectomy.
Cavernous nerve injury caused by different factors, including mechanical traction damage to the neurovascular bundle during mobilization of the prostate, as well as post-operative inflammation of the neurovascular bundle, is the main reason for post-surgical erectile dysfunction.
Different materials have been tested to reduce the rate of erectile dysfunction, in order to ultimately improve the quality of life for patients.
For example, sural nerve grafts have been used as interponates to replace completely resected neurovascular bundles in patients, leading, however, to rather unpredictable and unsatisfactory results (Scardino and Kim, “Rationale for and results of nerve grafting during radical prostatectomy”, Urology 2001, 57, 1016).
In animal experiments, a 2 mm rat cavernous nerve gap was either bridged with a biodegradable polyester conduit optionally containing collagen sponge (Hisasue et al., Cavernous nerve reconstruction with a biodegradable conduit graft and collagen sponge in the rat“, J Urol 2005, 173, 286), or with a cross-linked alginate gel sheet (Matsuura et al., Cavernous nerve regeneration by biodegradable alginate gel sponge sheet placement without sutures”, Urology 2006; 68, 1366).
However, as the human neurovascular bundle is composed of a heterogeneous network of nerve fibers and blood vessels, unlike the cable-like structure in the rat, results cannot be transferred from the rat model to the clinical situation.
Modern surgery focuses on nerve-sparing techniques which results in an increased restoration of erectile function by preserving the integrity of the neurovascular bundles.
While mechanical damage to the neurovascular bundle can be minimized by the experienced surgeon, the post-surgical inflammation remains a problem, which has to be addressed.
For example, a biodegradable polyester membrane containing brain-derived neurotrophic factor and adipose-derived stem cells has been tested in a rat cavernous nerve crush injury model, and an improved erectile function was observed compared to the non-cell containing group (Piao et al., “Therapeutic effect of adipose-derived stem cells and BDNF-immobilized PLGA membrane in a rat model of cavernous nerve injury”, J Sex Med 2012, 9, 1968).
The application of growth factors and anti-inflammatory substances to preserve and regenerate the prostatic neurovascular bundle has been further advanced by the use of dehydrated human amnion/chorion membranes as source of neurotrophic factors and cytokines.
In the clinical setting, at one month post-surgery, approximately 30% of the patients regained potency and urinary continence in both the treated and control groups while at three months, approximately 70% of the patients in the treated group were potent and 95% continent, with slightly lower numbers observed for the control group (Patel et al., “Dehydrated human amnion/chorion membrane allograft nerve wrap around the prostatic neurovascular bundle accelerates early return to continence and potency following robot-assisted radical prostatectomy: propensity score-matched analysis”, Eur Urol 2015, 67, 977).
As both the manufacture process and the regulatory approval and commercialization of a medical device in combination with growth factors and cellular components are demanding and expensive processes, there is still a need for simple technical solutions, preferably based on biocompatible and biodegradable components, that can efficiently support the early return of continence and potency in patients following prostatectomy.